drm/ingenic: Use drmm_add_final_kfree

With this we can drop the final kfree from the release function.
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Paul Cercueil <paul@crapouillou.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-17-daniel.vetter@ffwll.ch

drivers/gpu/drm/ingenic/ingenic-drm.c

@@ -23,6 +23,7 @@
 #include <drm/drm_fourcc.h>
 #include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_irq.h>
+#include <drm/drm_managed.h>
 #include <drm/drm_of.h>
 #include <drm/drm_panel.h>
 #include <drm/drm_plane.h>
@@ -490,11 +491,8 @@ static irqreturn_t ingenic_drm_irq_handler(int irq, void *arg)
 
 static void ingenic_drm_release(struct drm_device *drm)
 {
-	struct ingenic_drm *priv = drm_device_get_priv(drm);
-
 	drm_mode_config_cleanup(drm);
 	drm_dev_fini(drm);
-	kfree(priv);
 }
 
 static int ingenic_drm_enable_vblank(struct drm_crtc *crtc)
@@ -639,6 +637,7 @@ static int ingenic_drm_probe(struct platform_device *pdev)
 		kfree(priv);
 		return ret;
 	}
+	drmm_add_final_kfree(drm, priv);
 
 	drm_mode_config_init(drm);
 	drm->mode_config.min_width = 0;